may be you have more than one languages installed.try typing alt+shift and retry to enter the ''.it might be on french in which case the '' sympol is 2 key's left from enter.
i installed win 10.it could not finish the instalation so i tried to put it back to win 7.i tdidnt work so i tried to boot from a usb both os's .the bios regognises the usb but it is unable to boot from it.